Rock drill



Oct. 24, 1961 A. D. PAuLsoN 3,005,443

ROCK DRILL Filed Feb. 29, 1960 2 Sheets-Sheet 1 Oct. 24, 1961 A. D. PAULSON ROCK DRILL 2 Shee ts-Sheet 2 Filed Feb. 29, 1960 INVENTOR LOREE AD. PAULSON BY\ H I s AT- 3,005,443 ROCK DRILL Loree A. D. Paulson, Phillipsburg, N.J., assignor to Ingersoll-Rand Company, New York, N.Y., a corporation of New Jersey Filed Feb. 29, 1960, Ser. No. 11,539 8 Claims. (Cl. 121-25) This invention relates generally to percussively operated tools, and more particularly to an improved type of paving breaker to break concrete and the like.

It is commonly known that over the years various attempts have been made to increase the impact force of the paving breaker in order to increase its breaking rate. However, these attempts have resulted in the development of the present type commonly known paving breaker in which, apparently the operators ability to hold the tool during operation has not been sufliciently taken into consideration.

In order to increase the breaking rate of the paving breaker it is desirable to increase its impact force, however, when the impact force is increased the frequency of operation of the tool is in general unaltered or increased, resulting in an increased reactive force of the tool relative to the operators ability to hold the tool with ease. Actual tests have shown that, when the impact force of the tool is increased, in order to increase the breaking rate of a paving breaker, the frequency of operation of the tool must be substantially reduced to match the reactive force to the operators ability to provide such force to hold the tool with ease.

According to this invention the reduction in frequency of operation of the tool and the increase of its impact force have been achieved by the provision of a time delay valve which controls the actions of the piston in the tool to produce a greater impact force, and a lower frequency of operation, compared to the presently known common type paving breaker.

It is then the principal object of this invention to provide a percussively operated tool adapted to match the operators ability to hold the tool.

Another object of this invention is to provide a percussively operated tool in which the impact force is greater than that of the commonly known types of percussively operated tools.

Yet another object of this invention is to provide a percussively operated tool adapted to produce a controlled lower frequency of operation, compared to the commonly known type paving breaker.

Still another object of this invention is to provide a percussively operated tool in which the impact energy is more effectively utilized than heretofore practiced.

These and other objects and advantages of this invention will more fully appear from the following description made in connection with the accompanying drawings in which FIGURE 1 shows a part of a paving breaker in longitudinal section, illustrating a preferred embodiment of the invention. The piston of the paving breaker is shown in its extreme forward position.

FIG. 2 shows the position of the piston of the paving breaker shown in FIG. 1 in substantially its extreme rearward position to demonstrate the corresponding positions of the valve relative to those of the piston.

FIGS. 3, 4, 5, 6, 7 and 8 show cross sectional views along the lines 3--3, 44, 55, 6-6, 7-7 and 88, respectively, of FIG. 1 and looking in the direction of the associated arrows.

Referring now more particularly to the drawings, the tool according to the invention includes a casing 10 having a bore 12 and a pressure fluid actuated piston 14 reciprocable in the bore 12. The casing 10 comprises a 3,005,443 Patented Get. 24, 1961 back head 16 and a front head 18, the forward end of the front head 18 being adapted to receive an anvil block 20 and asteel 22, the anvil block 20 to be struck by the piston 14 and to transmit the impacts to the steel 22. In the back head 16 of the tool is provided a common type throttle valve 24 which controls the supply of pressure fluid admitted from a source of supply (not shown) and through a hose 26 to the tool.

In the rear end portion of the back head, a valve 28 is positioned to serve as a distributing member to distribute the pressure fluid alternately to the forward and rearward end portions of the bore 12 to reciprocate the piston. It is to be noted that the valve 28 also serves to delay the piston action during a predetermined period of a cycle of operation of the piston. In addition thereto the valve 28 is adapted to freely exhaust the forward end portion of the bore 12 during the entire impact stroke of the piston 14 in order to permit the piston to strike a harder blow to the anvil block 20 relative to the blows in the common type paving breaker.

The valve 28 is of the spool type and is in the form of a flanged sleeve, comprising a sleeve 30 provided with a flange 32 connected to the upper end of the sleeve 30. The flange 32 has two pressure surfaces, 34 and 36, 34 at the upper end and 36 at the lower end thereof, respectively. The exterior of the lower end portion of the sleeve 30 is provided with an annular undercut 38. The interior of this portion of the sleeve 30 has a smaller diameter than the diameter of the upper end portion, and, between the upper and lower end portions of the sleeve 30 is formed a pressure surface 40 the area of which is smaller than the area of the pressure surface 36 formed on the lower end of the flange 32.. The upper end portion of the sleeve 30 is provided with two sets of ports 42 and '44, each set of ports being radially drilled through the sleeve 30.

The valve 28 is slidably fitted in a valve cage 46, the valve cage having annular undercuts 48, 50 and 52 which cooperate with the undercut 38 in the valve 28 to distribute the pressure fluid to operate the piston, as will be explained in detail hereinafter. At the upper end of the valve cage 46 a flanged sleeve type retainer 54 is positioned and adapted such that the upper end portion of the valve 28 slidably fits between the skirt 56 of the sleeve type retainer 54 and the valve cage 46. A number of ports 58 is radially drilled in the skirt 56 of the retainer 54- and positioned such to register with the ports 42 when the valve 28 is in its extreme forward position.

Between the lower end 60 of the flange of the retainer 54 and the upper end 34 of the flange 32 of the. valve 28 a cavity 62 is formed which is communicated with the interior of the bore 12 of the casing 10 through a passage 64 drilled in the casing. Another passage 66 is provided and communicates the undercut 52 of the valve cage 46 with the interior of the upper end portion of the bore 12. This passage 66 has an extension 68 which communicates the passage 66 and the undercut 52 with the interior of the bore 12. A bleeder passage 70, positioned at the upper end portion of the bore 12, communicates the bore 12' with the passage 66, the position of this bleeder passage 70 being such to permit an air cushion to be formed at the upper end of the bore 12 and to prevent the piston 14 from striking the lower end 72 of the valve cage 46 when the piston 14 is moved upwardly. The interior of the lower end portion of the bore 12 is communicated with the undercut 48 through a passage 74 drilled in the casing 10, this passage acting as an inlet and as a discharge for the lower end portion .of the bore 12. a

In operation, the tool functions as follows: The piston 14, as shown in FIG. 1, is in its extreme forward position after delivering its impact blow to the anvil block 20,

The valve 28 is in its extreme forward position permitting pressure fluid that is admitted by the throttle valve 24 to flow through a passage 25 and through ports 27 in the back head 16, through the interior of the retainer 54 and the valve 28, and through the ports 44, the undercut 48, and passage 74 to the interior of the forward end portion of the bore 12. It is to be noted that the passage 44 is adapted to restrict the flow of air therethrough in order to move the piston 14 slowly rearwards relative to the speed of the impact stroke of the piston 14.

When the piston is moved rearwardly past the portion 1590f the passage 68, a part of the supply of pressure fluid conducted through the passage 74 will be discharged through the passages 68, 66, and through the undercut 52 into the undercut 59 from where it is discharged through the exhaust 76. This discharge through the passage 68 is determined by the cross sectional area of the portion 69 of the passage 68 and is made such to create a pressure differential between the pressure forward of the piston and the pressure rearward of the piston that will cause the piston 1 to move at a substantially low speed towards its extreme rearward position from its position rearward of the passage portion 69. This piston action is thus delayed for a predetermined period of time in order to reduce the frequency of operation of the tool. It is to be noted that when the piston 14 approaches its extreme rearward position the fluid rearward of the piston is first discharged through the portion 67 of the passage 66 and then through the bleeder passage '70 whereafter the fluid rearward of the piston is trapped to form a cushion to prevent the piston 14 from striking the lower end 72 of valve cage 46.

While the piston is moving slowly rearwards pressure fluid flows through ports 58 and ports 42 into the portion of the cavity 62 forward of the pressure surface 36 and as the ports 58 are adapted to restrict the flow of pressure fluid into this cavity 62 the pressure herein will build up gradually. As the pressure surface 36 on which the force of the pressure fluid is gradually exerted is larger in area than the pressure surface 40, as mentioned before, the greater force on the pressure surface 36 will overcome the force on the pressure surface 40 and the valve 28 will be forced rearwardly. It is to be noted that, after the valve 28 is moved rearwardly, the pressure fluid in the space 37 forward of the pressure surface 36 is vented through a bleed off passage 80 to the atmosphere, the bleed ofl": passage 80 being positioned to be uncovered by the flange 32 of the valve 28 only when the valve 28 has been moved to its extreme rearward position. When the valve 23 is moved to its extreme rearward position the forward end of the valve will uncover the passage 66 to permit the pressure fluid to flow therethrough, first through the bleeder passage 70 for initial forward movement of the piston 14 and then through the passage portion 67 into the interior of the rear end portion of the bore 12 to force the piston 14 forwardly on its impact stroke.

When the piston 14 moves forwardly on its impact stroke the exhaust of the interior of the forward end of the bore 12 is conducted through the passage 74, undercut 48 and into the undercut 50, and therefrom into the exhaust passage '76.

During the impact stroke of the piston 14, the piston uncovers the opening of the passage portion 65 and permits the pressure fluid to flow from the passage portion 6'7 into the passage portion 65 and through the passage 64 into the cavity 62 between the forward end 6%) of the retainer flange 54 and the rearward end 34 of the valve flange 52. As the areas of the pressure surfaces 34 and 40 are greater than the area of the forward end 78 of the valve 28 the greater force on the areas 34 and 40 will force the valve 23 forwardly, the valve to reach its extreme forward position after the piston 14 has struck the anvil block 20, this to insure a free exhaust of the fluid forward of the piston. It is to be noted that, after the valve 28 is moved forwardly, the pressure fluid in the cavity 62 is vented through a bleed oil passage 82 to the atmosphere, the bleed off passage 82 being positioned to be uncovered by the flange 32 of the valve 28 only when the valve 28 has been moved to its extreme forward position.

When the valve 28 is in its extreme forward position the cycle of the piston 14 and that of the valve 28 is repeated.

The speed of the piston motion is determined by the size of the ports 58 in the retainer 54 as well as by the size of the ports 44 in the valve 28, and consequently, the time that the piston is delayed before-starting its working stroke, as described hereinbefore, is also determined by the size of the ports 58 and 44.

Actual tests have shown that, for the .most effective use of the tool, the time interval, from the moment the piston is moved from its normal rearward position until the moment the piston strikes the anvil block or steel as compared to the time interval from the moment the piston strikes the anvil block or steel until the moment the piston is moved from its normal rearward position, is preferably within the ratio range of from 1:2 to 1:5. It is to be noted that the frequency of the tool is held within the aforementioned limits, because, outside these limits the tool will operate at a frequency that is either too high or too low relative to the holding capacity of the operator and to the braking rate of the tool.

It is to be understood that various changes and modifications may be made in the preferred form of my invention, as shown and described hereinbefore, without departing from the spirit of my invention as set forth in the appended claims.

I claim:

1. A pressure fluid actuated percussive type tool including a casing, a pressure fluid actuated piston reciprocable forwardly and rearwardly in said casing, a working implement positioned to be actuated by said piston, fluid distributing means to distribute fluid to the interior of the opposite end portions of said casing to reciprocate said piston, and means to control the distribution of fluid to move said piston rearwardly substantially slower than in the forward direction, and to momentarily delay the piston during its rearward stroke.

2. A pressure fluid actuated percussive type tool including a casing, a pressure fluid actuated piston reciprocable in said casing, a working implement extending in said casing to be actuated by said piston, a valve in said casing to distribute pressure fluid to the interior of the opposite end portions of said casing to reciprocate said piston and operable to exhaust the fluid forward of said piston during the entire forward stroke of said piston, and means to restrict the supply of pressure fluid to the interior of the forward end portion of the casing to move said piston rearwardly substantially slower than in the opposite direction.

3. The tool claimed in claim 2 in which said means includes supply and exhaust passages in said casing and said valve, said passages being positioned to be controlled by the movement of said piston to actuate said valve and said piston.

4. A pressure fluid actuated percussive type tool including a casing, a pressure fluid actuated piston reciprocable in said casing, a working implement positioned to be actuated by said piston, a valve in the casing to distribute pressure fluid to reciprocate said piston and operable to exhaust the fiuid forward of said piston during the entire forward stroke of said piston and to restrict the supply of pressure fluid to the interior of the forward end portion only of the casing to move said piston in one direction substantially slower than in the opposite direction.

5. A pressure fluid actuated percussive type tool including a casing, a pressure fluid actuated piston reciprocable in said casing, a working implement extending into said casing to be actuated by said piston, a valve on the tool to distribute fluid to the interior of :the .opposite end portions of said .casing to reciprocate said piston, fluid supply and exhaust ports in the casing and in the valve, said fluid supply and exhaust ports being positioned to be controlled by the movement of said valve to restrict the flow of pressure fluid to the interior of one end portion only of said casing to move said piston in one direction at a substantially slower speed than in the opposite direction, and means other than gravity of said piston to cause a substantial interval between successive strokes of said piston.

6. The tool claimed in claim in which said means includes a fluid supply passage in the casing positioned to supply pressure fluid to the interior of the forward end portion of said casing to actuate said piston rearwardly, and an exhaust passage positioned to exhaust fluid forwardly of said piston only when said piston is substantially in its extreme rearward position, said supply and exhaust being adapted such to create a pressure forward of said piston large enough to hold said piston during a predetermined period of time before said piston is moved forwardly.

7. A pressure fluid actuated tool comprising, a casing, a fluid actuated piston reciprocable in said casing, a single fluid actuated reciprocatory valve positioned in said casing to distribute fluid to reciprocate said piston, and means to control the distribution of fluid to reciprocate said piston and said valve by movement of said piston and 6 said valve, said means including fluid supply and exhaust passages in the casing and in the valve, said fluid supply and exhaust passages being positioned to be controlled by movement of said piston to move said valve in one direction only, and means to move said valve in the other direction.

8. The tool claimed in claim 7 in which said means includes two pressure surfaces on said valve, only one of said pressure surfaces being constantly exposed to pressure fluid to constantly urge said valve in one direction, the other pressure surface to move said valve in the other direction having an area larger than the said one of said pressure surfaces and being exposed to pressure only after said valve is moved in one direction controlled by the movement of said piston.

References Cited in the file of this patent UNITED STATES PATENTS 1,068,711 Taylor July 29, 1913 1,789,698 Curtis Jan. 20, 1931 1,861,984 Slater June 7, 1932 2,093,088 Mack Sept. 14, 1937 2,252,711 Gartin Aug. 19, 1941 2,312,367 Gartin Mar. 2, 1943 

